The S&P 500 eked out a gain of 2.34 points, to end at 1,762.11, after setting a new all-time high of 1,765.01 during intraday trading. The Nasdaq slipped 3.23 points, to finish at 3,940.13.

The CBOE Volatility Index (VIX), widely considered the best gauge of fear in the market, closed above 13.

"It's not a big move to get there," said Mark Luschini, chief market strategist at Janney Montgomery Scott of the S&P 500 run to another record high. "But certainly we continue to march higher. Earnings are better than expected, the beats are running about 63 percent, but also actual earnings growth, and even the revenue numbers are feeding expectations."

All three averages are poised to close sharply higher for the month, with the S&P 500 and Nasdaq up more than 4 percent each.

Among key S&P sectors, materials led the decliners, while defensive areas such as consumer staples and telecoms ended higher.

"Investors are waiting for more in terms of earnings and economic reports," said Michael Sheldon, chief market strategist at RDM Financial Group. "The tone of the market overall remains positive, but the rate of gains may slow down from the rate we've seen over the past several weeks."

Among earnings, Merck posted earnings that edged past expectations, but revenue was slightly short of consensus. The drugmaker also reported full-year forecast above current analyst forecasts, though the company warned its third quarter results were hurt by the expiration of various patents, and by negative currency impact.

Bristol-Myers Squibb jumped after Morgan Stanley upgraded the pharmaceutical company to "overweight" from "equal weight." Over the weekend, Bristol-Myers provided additional data to its lung cancer treatment, which showed a 24 percent chance of two-year survival, compared to 14 percent in June.

"If we end up with a 5 to 6 percent growth rate, that's a pretty good earnings season these days," said Dan Greenhaus, chief global strategist at BTIG. "[But] the one issue our clients are starting to hone in on is the manner in which that earnings beat has picked up and that includes a combination of stock buybacks, lowered tax rates and a couple other one-time items. If you were more bearishly inclined, you could be a little more skeptical."

So far, half the S&P 500 companies have posted quarterly results, with 69 percent of firms topping earnings expectations and 54 percent beating revenue forecasts. If all remaining companies post earnings in line with estimates, earnings will be up 3.4 percent from last year's third quarter.

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JCPenney spiked more than 8 percent after the retailer reaffirmed its expectations for positive same-store sales coming out of the third quarter, according to Reuters. Other retailers including Kohl's, Nordstrom and Macy's also gained following the announcement.

Netflix eased off session lows after the movie-streaming site announced a content licensing agreement with CBS, in which all eight seasons of Showtime's drama Dexter will become available for U.S. subscribers.

On the economic front, industrial production rose 0.6 percent in September, logging its largest increase in seven months, according to the Federal Reserve. Economists polled by Reuters had expected industrial output would rise 0.4 percent.

Meanwhile, pending home sales fell 5.6 percent to 101.6 in September, according to the National Association of Realtors, logging the fourth-monthly decline. Economists surveyed by Reuters had expected a slightly increase.

"There's almost no chance on the upcoming meeting that [the Fed] puts some type of a date certain," said Greenhaus. "They have to be concerned about market expectations, but tapering in December or March isn't meaningfully going to change the larger story."

The Treasury sold $32 billion in 2-year notes at a high yield of 0.323 percent. The bid-to-cover ratio, an indicator of demand, was 3.32, versus a recent average of 3.31. In recent weeks, the yield on the 10-year has declined from a peak of 3.00 percent recorded on September 5 back towards the key 2.50 percent mark.